Computer networks may be separated into domains that contain groupings of computing devices, such as personal computers, servers, routers, switches, and/or firewalls, administered as a unit with common rules and procedures. The Internet is one type of a computer network. In order to access the full range of information and functionality available on the computer network, computing devices may send messages to computing devices in other domains.
Communication between computing devices in different domains typically travels through a network gateway. The network gateway is one type of computing device that may serve as a connection, or portal, between domains. The first network gateway a message passes through is called a first-hop gateway. Reliability and capacity of network gateways, in particular first-hop gateways, can affect communication, or traffic, on the computer network. Network gateways, like other computing devices, occasionally fail. Network gateways can also become bottlenecks for traffic traveling from one domain to another.
Traditional computer networks address a problem of network gateway failure by arranging network gateways in redundant pairs. A first network gateway is the primary route for network traffic and a second network gateway is a backup. If the primary network gateway fails, all network traffic that was going through the primary network gateway is rerouted through the backup network gateway. This arrangement of one primary network gateway to one backup network gateway creates 1:1 resilience. Typically, in the primary/backup network gateway arrangement, backup network gateways remain idle until the primary network gateway fails. Thus, the capacity of a backup network gateway is not available to reduce bottlenecks, and approximately half of all network gateways in a network (i.e. the backup network gateways) are idle at any time.
Another problem in traditional computer networks is that each computing devices in a domain sends a stream of messages to an associated primary network gateway to keep the association with the network gateway alive and to monitor the health of the network gateway. These messages themselves create network traffic that can slow other communications. In a large domain, these messages may consume a significant portion of the total capacity of a network gateway. Conventional routing protocols such as Routing Information Protocol (RIP), Open Shortest Path First (OSPF), and Hot Standby Routing Protocol (HSRP), make use of the primary/backup network gateway arrangement to select a first-hop gateway. Thus, the existing routing protocols all share the above deficiencies.